In many applications of X-ray imaging, and especially in medical imaging applications, it is highly desirable to minimize the total X-ray dose delivered during imaging to the subject or object being imaged. Since X-rays travel substantially in straight lines, X-rays emitted from the X-ray source (or sources) directed away from any X-ray detector in the system are useless for imaging. Such useless radiation is typically blocked by providing an X-ray collimator near the X-ray source that passes radiation directed toward the detector(s) and blocks other radiation.
Various X-ray imaging systems have been considered in the art, and a corresponding variety of X-ray collimation approaches for imaging have also been considered. For example, in U.S. Pat. No. 4,315,157, an imaging approach having a single X-ray source and multiple well-separated detectors is considered. A collimator is employed to block radiation that otherwise would pass through the patient and strike the dead spaces between the detectors. Fan beam systems (e.g., as in U.S. Pat. No. 6,229,870) are commonly employed, where a collimator having vanes defines several parallel thin fan-shaped beams.
Conventional X-ray collimators typically provide vanes to define fan beams and/or high aspect ratio channels to define narrow beams, e.g., as considered in US 2004/0120464. Collimators having a large rectangular aperture matched in shape to a rectangular detector array are considered in US 2004/0028181. In U.S. Pat. No. 5,859,893, a system having multiple source locations and multiple detectors is considered. The corresponding collimator has independent high aspect ratio channels defining beam paths from each source to each detector.
However, when an X-ray imaging system has multiple sources and multiple detectors, conventional X-ray collimation approaches (e.g., providing independent channels for each source to detector path) can encounter a hitherto unappreciated difficulty. More specifically, providing such independent channels in the collimator can lead to a situation where the X-ray source spacing is forced to be undesirably large.
Accordingly, it would be an advance in the art to provide an X-ray collimator for multi-source, multi-detector imaging systems that can provide reduced source spacing.